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Explanations for the 2014-2015 Official Step 1 Practice Questions

Using the official 2014-15 “USMLE Step 1 Sample Test Questions,” (cached version here) I’ve written explanations and take home points for each of the 138 questions (the “Free 150”). The 2015-16 set has no new questions (a few have actually been removed), so this is still current. I can’t reproduce the questions themselves of course as they’re uber-copyrighted.

An asterisk means it’s a new question (of which there are around 84). The questions and explanations for last year (2013-14) can still be found here.

The new 2016 set is out and has around 50 new questions, which are discussed here.

Block 1

C – Acute abdominal pain in a fertile woman is very frequently going to be an ectopic question. Associated fun fact: the most common cause of secondary amenorrhea is pregnancy.

E – Parents can be overly protective of their children with chronic diseases (diabetes, lupus, etc). This child doesn’t have SCID, so going to school isn’t going to kill them. The child is in overall reasonable health with only mild symptoms. Vulnerable child syndrome is characterized by unreasonable parental anxiety. *

B – You are seeing a tube inside of a tube in the pathology specimen. Yes, look again: bowel within bowel. Intussusception. Currant jelly stools. Classic history (sudden onset colicky pain, palpable mass). Now, a right lower quadrant lesion that causes pain and hematochezia, particularly in a child? Then you would get to think of Meckel’s (with its rule of 2′s).

F – While staph aureus is the most common cause of hematogenous osteomyelitis in children, Salmonella is the most frequent cause for patients with sickle cell anemia (a test favorite). I think I may have even had this fact tested twice on my Step.

D – Reye’s syndrome is the reason why children don’t receive aspirin (except to treat Kawasaki’s disease, of course). Reye’s syndrome is characterized by vomiting followed liver damage (hepatic steatosis and hepatomegaly) and encephalopathy beginning with irritability and aggressive behavior and potentially progressing to coma.*

B – Bisphosphonates work by decreasing osteoclast activity (thereby reducing bone resorption). Choice F is the opposite of how estrogen therapy works (RANKL is found on osteoblasts, and its activation triggers osteoclasts and stimulates bone resorption).*

B – Azotemia, hemoconcentration, and hypotension/tachycardia are all results of dehydration. This may lead to acute renal failure if allowed to continue (but this diagnosis requires a change in creatinine of 0.3).

A – Phenylephrine is an alpha-agonist nasal spray and oral medication that often shows up on exams. Oxymetazoline (Afrin) is a similar alpha-agonist nasal spray. Pseudoephedrine is another decongestant with a similar MOA that’s less common now that it’s a federally monitored component of methamphetamine production. Topical alpha agonist decongestants are physically addictive and can cause miserable rebound congestion (rhinitis medicamentosa). Systemic formulations can cause hypertension and worsen prostate problems by causing prostatic smooth muscle constriction. Just remember that tamsolusin (Flomax) is an alpha-5a antagonist, which relaxes prostate muscle.

A – She has nephrogenic diabetes insipidus (large volume dilute urine production that cannot be reversed with the administration of exogenous vasopressin). Aquaporins are the water channels that allow for the reabsorption of free water from the collecting ducts and the production of concentrated urine.

A – The p-value corresponds to the likelihood of a type I error (a false positive). A lower p-value means a lower acceptable likelihood of obtaining the same results by chance, and thus, significant results can be reported more confidently (a 1% false positive rate instead of a 5% rate).*

A – Gonorrhea can change its pilus, which is responsible for adhesion to host cells and the main antigen to which the host mounts an immune response. Neisseria gonorrhoeae is able switch out different pilin genes, and for this reason, prior infection does not confer long lasting immunity.*

B – Crossed findings means a brainstem lesion. Left (ipsilateral) tongue, right-sided (contralateral) weakness means the exiting left hypoglossal nerve has been affected (within the left medulla). B is the pyramid where the corticospinal tract runs to control muscles (prior to the decussation). This is known as medial medullary syndrome or Dejerine syndrome.

A – p53 is the quintessential tumor suppressor (it activate apoptosis). Carcinogenesis of HPV is caused by insertion of the virus into the host DNA and producing a protein which binds with an essential p53 substrate, functionally inactivating the p53 and its apoptotic cascade. C (transactivation/TAX) is how HIV and HTLV cause cancer. E (cmyc translocation) causes Burkitt lymphoma.*

A – It’s the antibodies to surface antigens that are protective. Hemagglutinin is a surface antigen that is responsible for clumping RBCs in vitro.

A – All the vesicles contain the same viral infection, so all should have the same appearance on gel. Choice D is what a gel looks like without using a restriction enzyme digest (no discrete bands of specific weights).

B – Post-streptococcal glomerulonephritis is caused by the deposition of circulating immune complexes (a type III hypersensitivity and a test-favorite).*

A – As always, it’s almost better to ignore the pictures when possible. This gentleman has a peptic ulcer, which we know is caused predominately by H. pylori infection. H. pylori produces proteases and particularly urease, which allow it to increase the pH of the its local environment by cleaving urea into ammonia, which is toxic to gastric mucosa. The picture demonstrates H pylori, which are evident with silver staining.*

D – Schistosomiasis is a parasitic worm particularly endemic in Africa (Egypt in particular comes up a lot on questions) that is most associated with chronic cystitis. Calcifications of the bladder wall are essentially pathognomonic. Chronic infection is associated with an increased risk of squamous cell carcinoma of the bladder (as opposed to the usual urothelial/transitional cell).*

E – This patient has chronic kidney disease, as indicated by elevated serum creatinine/BUN and evidence of anemia of chronic disease (normochromic normocytic). Poorly functioning kidneys do not hydroxylate 25-Dihydroxycholecalciferol to 1,25-Dihydroxycholecalciferol well nor produce adequate erythropoietin (hence the CKD-related anemia). Patient’s with CKD development thus develop secondary hyperparathyroidism due derangements in phosphate excretion and inadequate Vitamin D activation resulting in hypocalcemia. Thus, we should expect to see low calcium, high phosphorus, low 1,25 vitamin D, and low Epo, which is E.*

C – The meningitis diagnosis is a giveaway. Your job is to know two things: 1) the common pathologic organisms in different age groups or 2) that Neisseria is a gram negative diplococcus.

B – To amplify tiny fragments of DNA in order to detect their presence, we use PCR. The question is a description of the process. Southern Blots are used to detect a specific DNA sequence within a DNA sample.*

C – Hookworm infection can cause intestinal irritation leading to chronic GI blood loss and iron deficiency anemia. An otherwise healthy boy who lives in rural Mississippi, probably playing in the mud in his bare feet like a hillbilly? That’s the kind of kid who would get hookworm. Treatment is mebendazole (albendazole would also be fine. These are your go to choices for anti-helminthics).*

A – Androgen insensitivity is caused by a defective androgen receptor. DHT is responsible for creating male genitalia during fetal sexual development. The default human gender is female. So a genetically male patient with complete androgen insensitivity is externally phenotypically female. Lack of response to adrenal androgens prevents hair formation during puberty (adrenarche).*

D – You need to memorize the list of drugs that induce and inhibit CYP450. Warfarin has oodles and oodles of drug reactions for this reason with potentially dire consequences.

C – Leydig cells make testosterone. Leydig cell tumors aren’t always physiological active, but those that are can cause masculinization. Granulosa cell tumors, on the other hand, sometimes produce estrogen. Teratomas are oddballs that typically have fat, hair, teeth, etc. Thecomas will not be on your test. Ovarian carcinoid is highly unlikely to show up on your test, but if it did, it would likely present with a classic carcinoid syndrome.*

B – This patient has cystic fibrosis. The combination of respiratory and GI issues is classic and caused by ineffective chloride transport and consequently thick exocrine secretions, which clog up the airways and the pancreatic ducts.

E – Polycythemia Vera is the red blood cell cancer. Symptoms are related to hyperviscosity of the increased hematocrit. A classic symptom of polycythemia vera is pruritus, typically with exposure to hot water (e.g. the shower). Super high hematocrits are indicative. Low EPO means that the body is responding appropriate by trying to tone down RBC production (which continues autonomously in PCV). JAK2 mutation, test favorite. The classic treatment is bloodletting, like they used to do for everything back in the middle ages.*

D – Sensitivity rules things out. It’s TP / (TP + FN). So in order to calculate the sensitivity of this test, we need the true positives (the 90 with cancer) and the false negatives: the patients for whom the test is negative but actually do have prostate cancer. That’s D.*

C – Polyarteritis nodosa is that only one that makes sense in explaining the diffuse constellation of symptoms in this question. It affects small and medium arteries, including those involving the skin, heart, kidneys, GI tract, etc. On imaging, a “rosary sign” of small aneurysms strung like beads on a rosary is sometimes mentioned. The biopsy shows an inflamed artery (arteritis). Angiodysplasia typically causes painless GI bleeding (like that seen in diverticulosis). Kawasaki disease is in children (5 days of fever, strawberry tongue, etc). Takayasu arteritis involves big arteries, like the aorta, carotids, and subclavians (with classically diminished upper extremities pulses, hence “pulseless disease”). Thromboangiitis obliterans is also known as Buerger’s disease, a vasculitis seen essentially exclusively in smokers that causes severe peripheral arterial disease (legs much more so than hands). Wegener’s is typified by the combination of renal and lung (and sinus) findings in conjunction. The picture would should granulomas, and C-ANCA would likely be positive, because it’s a board exam.*

E – Androgens stimulate sebaceous glands and cause acne. In girls, this is primarily due to adrenarche (DHEA/DHEAS androgen production made by the adrenal gland the zona reticularis). Boys can also blame testosterone from gonadal puberty (pubarche).*

B – Six-year-olds typically understand the finality of death. Infants have no understanding, whereas preschool age children often think of deaths in reversible or metaphorical terms.

B – Thiazides (typically used as antihypertensives) also increase calcium resorption in the distal tubule and are therefore useful in preventing calcium oxalate stone formation in patients with hypercalciuria (the mechanism is not really worth learning). Thiazides block the Na-Cl symporter, as opposed to loop diuretics, which block the triporter, and acetazolamide, which blocks carbonic anhydrase in the proximal tubule.*

A – Pyknosis and nuclear fragmentation are part of the process of apoptosis.

A – Acetaminophen (Tylenol) can cause fulminant hepatic failure in overdose. This will probably be on your test.

A – The infraspinatus and teres minor are responsible for external rotation. Both the infraspinatus and supraspinatus muscles are innervated by a suprascapular nerve.*

C – Filgrastim is a granulocyte colony stimulating factor, which are drugs use to increase white blood cell count in patients with leukopenia. Leucovorin (folinic acid) sounds like it would also be right; it’s used to prevent bone marrow suppression in patients taking methotrexate. Darbepoetin (like erythropoietin) is used to stimulate red blood cell production.*

F – A Nystatin mouthwash is the treatment of choice for oral candidiasis. It’s topical, it’s easy, it works. For tongue thrush, the patient can spit it out (and therefore no chance for side effects). For pharyngeal/esophageal candidiasis, the patient can “swish and swallow.” Inhaled cortisteroids, particularly if used without an air chamber (spacer) can cause local immune suppression when contacting the oral mucosa, leading to thrush.*

A – Turner syndrome (you may remember lymphedema of the neck by another name: cystic hygroma). The 45,X gives it away though anyway. Mosaic Turner’s syndrome and the mosaic trisomies result from nondisjunction during mitosis. In total monosomy/trisomies, the cause is nondisjunction during meiosis. Uniparental disomy is essentially only tested via the Prader-Willi and Angelman syndromes (chromosome 15).

D – The baroreceptors are stretch receptors (the more fluid in the vessel, the more they fire). So a patient with hemorrhagic shock will see a decrease in the baroreceptor firing rate. Activation of RAAS will result in increased vascular resistance (vasoconstriction) in order to maintain blood pressure. And capillaries, such as those in the kidney, will be primed for resorption and not filtration (no one wants to pee out good dilute urine when they’re dehydrated). Likewise, systemic capillaries will prefer to hold onto plasma and not let it leak into the interstitium (third-spacing).*

Block 2

C – Home canned/bottled food is a buzz-term for botulism. That’s also why the bottles you buy in the store have that little pop up lid that stick out when you open it. If there’s botulism forming air in the bottle, then the lid pops up (and you shouldn’t eat it!). Botulinum toxin inhibits the release of acetylcholine (which actives the nicotinic receptors necessary for skeletal muscle contraction).*

C – Blood flow also increases during exercise. The more anaerobic metabolism you use and lactate build-up you have, the more hyperemia you need to clear out the waste products.

B – Aminoglycoside antibiotics (gentamycin, amikacin, etc) are powerful antibiotics especially useful for bad gram negative infections. Bad side effects are permanent hearing loss (ototoxicity) and renal failure. Both are important to know. Torsades de Pointes (choice E) can be caused by fluoroquinolones (e.g. cipro), as these drugs prolong the QT-interval.

C – This patient has hepatitis (elevated liver enzymes) due to active Hepatitis C infection. Hep C and HIV infection are both associated with intravenous drug use. While most patients with Hep A will clear the virus after their acute illness, Hep C causes chronic infection in 80% of patients, which may lead to cirrhosis over time (~20 years).*

C – Osgood-Schlatter is also known as apophysitis of the tibial tubercle. It’s due to chronic stress/irritation at the insertion of the patellar ligament on the tibial tubercle. It’s classically seen in teenagers doing repetitive vigorous activity (running, jumping). The radiograph demonstrates classic fragmentation of the tibial tubercle (which isn’t necessary to know to get the question correct).*

E – Gram positive rods in a diabetic foot wound (or a World War I soldier fighting in a trench) means Clostridium perfringens (the causative organism of gas gangrene). Crepitus means gas in the tissues, which is produced as a byproduct of its highly virulent alpha toxin.*

D – Antibiotic-associated diarrhea caused by clostridium difficile can be tenacious, difficult to treat, and even fatal. Alcohol-based rubs are not sufficient to kill the spores. Handwashing with soap is necessary, and equipment should be autoclaved to clean it.

A – Ballet dancers (wrestlers, models, ballet dancers, athletes who need to make weight, and particularly young women in general) all have eating disorders on Step 1. Folic acid is involved in the production of both red and white blood cells. Remember, low folate leads to macrocytic anemia and hypersegmented neutrophils. B12 deficiency (not an answer choice) leads to macrocytic anemia and neurological changes (including SCID in severe cases).

D – ITP causes immune-mediated consumption of platelets, hence the low platelet count and petechiae. The bone marrow biopsy results demonstrate that the body has appropriately increased platelet production, meaning that this is not a platelet production issue. While TTP has a similar acronym, it’s an entirely different disease with a classic pentad: thrombocytopenia (low platelet count), microangiopathic hemolytic anemia, altered mental status, renal failure, and fever.

G – Vincristine (a mitosis inhibitor) frequently causes peripheral neuropathy, which can be severe and irreversible. Other fun associations are Bleomycin with pulmonary fibrosis, Cyclophosphamide and bladder cancer, and Doxorubicin with dilated cardiomyopathy.*

D – The arrowed fluid is contained in a space behind the stomach but in front of the retroperitoneal structures (e.g. the pancreas), i.e. the lesser sac.*

D – People in their 60s don’t spontaneously become schizophrenic with any frequency for that to be ever be the correct answer. Likewise, Alzheimer’s is a slowly progressive cognitive decline (dementia), not an acute decline in mental status (i.e. delirium). This patient is delirious. Common causes in the elderly includes medications, infections, and being in the hospital (particularly the ICU).*

C – Anaphylaxis is treated with epinephrine.

C – Logic would dictate that a fracture of the inferior orbital wall might affect the infraorbital artery, and logic would be right.*

C -This is obviously a clinical trial. If you know you are getting a drug, then you are not blinded: it’s an open label trial. There is no randomization as there is only a single treatment group.*

C – Ah, you really want to pick A for cat scratch fever. But sore throat, adenopathy, and a positive Heterophile antibody test means mononucleosis (i.e. Mono), caused by Epstein-Barr Virus. The heterophile antibody test is due to a cross reaction with horse or sheep red blood cells, which are agglutinated in vitro by the antibodies in the patient’s serum.*

C – RSV, like all respiratory viruses, spreads via respiratory droplet. Babies are too young to wheeze because of asthma; they wheeze because of RSV.

D – Recurrent respiratory infections could be a lot of things. But then they mention the dextrocardia. Kartagener syndrome is the combination of situs inversus and defective cilia (due to a mutation in dynein), where the inability to effectively clear secretions results in recurrent sinusitis and bronchiectasis.

B – Choriocarcinoma is a much-feared complication of a molar pregnancy. It is a cancer of the bHCG-producing syncytiotrophoblasts found in the placenta.

B – This patient has symptomatic anemia. Its microcytic nature implies iron deficiency, which is most commonly due to occult blood loss. In the elderly, the concern is colon cancer. In a reproductive age female, iron deficiency is more commonly secondary to uterine pathology.

C – Factor V leiden is by far the most common heritable cause of hypercoagulability. Keep in mind that many “most likely” questions are actually asking you for the “most common” cause.*

D – This is rheumatic fever from group A strep pharyngitis. This is thankfully rare now, as we routinely treat Step throat with antibiotics. The cause of all the damage is due to cross-reactivity of Strep antigens with the tissues of the heart, joints, skin, and brain. Anti-streptolysin O (ASO) and anti-DNase titers will be high.

D – The Odds Ratio (OR), if you don’t simply have it memorized, is computed exactly as you would guess. It’s the odds of you getting a disease with the treatment (or risk factor) over the odds of you getting a disease without the treatment. In this case: 100/200 divided by 300/300 = 1/2.*

D – Rickets. “Pectus carinatum” is also known as “pigeon chest” (protruding sternum) and “bead-like enlargement of the costochondral junctions” is describing a rachitic rosary. Rickets is caused by vitamin D deficiency (either dietary or functional). Osteoblasts in patients with rickets lay down excess unmineralized osteoid, as they are less able to mineralize osteoid into mature bone without sufficient vitamin D.*

C – Lymphatic spread of disease moves through lymphatic channels from distal to proximal. The medial side drains to the superficial inguinal nodes. Much of the lateral side will stop at the popliteal nodes prior to ascending the thigh.

G – Sulfonylurea medications (glipizide, glyburide) stimulate the pancreas to secrete more insulin. For this reason, they are most efficacious early in the disease process when pancreas still has remaining functional reserve.

E – Those are sickle cells on the smear. LUQ pain on test questions almost always means splenic pathology. All sickle cell kids will eventually infarct their spleen.

E – Subacute combined degeneration (progressive peripheral sensory and motor loss) is a late sign of B12 deficiency, which is common in old people. On board exams, a geriatric patient who lives alone and may have a “tea and toast” diet is likely to have vitamin deficiencies, particularly of folate and B12.

D – An OR greater than 1 signifies increases odds/risk/likelihood. If the 95% CI range does not include 1, then the difference is statistically significant (though not necessarily clinically meaningful).*

C – Common sense is key, particularly for counseling-type questions. Patients have autonomy and can do whatever they want; it’s your job to explain the risks and benefits. The patients ultimately make their own treatment choices.

D – She is taking anabolic (androgenic) steroids as a performance enhancing drug. Being an athlete on Step 1 is never a good thing.*

A – A new blistering disease in an older person is typically going to be a pemphigus question. Then you just have to remember the difference between bullous pemphigoid vs pemphigus vulgaris. Bullous pemphigoid is characterized be the loss of hemidesmosomes that bind keratinocytes to the basement membrane, resulting in bulla (big blisters) in areas of friction, choice A. Patients with pemphigus vulgaris lose their desmosomes (which bind keratinocytes to each other), so that their skin is super friable, which results in ulceration. Mouth ulcers are more common in PV.*

B – This is a (prospective) case series. There is no control (and certainly no blinding).*

D – Pregnant patients should avoid fish and seafood products that are high in mercury. In general, this means that shellfish and big salt-water fish should be avoided (tuna, swordfish, shark, king mackerel, tilefish, etc)*

A – Air and fluid = hydropneumothorax. If that fluid is blood (s/p stabbing), it’s a hemopneumothorax. Lack of mediastinal shift indicates that it’s not under tension.*

B – Finasteride (aka Propecia) is used for male pattern baldness and prostate hypertrophy. It’s a 5-alpha-reductase inhibitor, which prevents the conversion of testosterone to dihydrotestosterone (DHT).

B – Gout, gout, gout. Allopurinol helps prevent flares but does nothing to treat them. Treatments of choice for an acute flare are NSAIDS or colchicine.

E – Splitting is an immature defense mechanism often employed by patients with borderline personality disorder. When splitting, a person fails to see others as capable of having both positive and negative qualities; at any given time, it’s all or nothing.*

F – Prolonged bleeding time with normal clotting factors (as evidenced by normal PT/INR and PTT) and a sufficient platelet count is going to be von Willebrand disease, the most common hereditary coagulation abnormality, which by either deficiency or mutation results in dysfunctional platelets. A temporary treatment for uncontrolled bleeding is vasopressin, which causes for addition vWf release. Factor VIII concentrate is a more dramatic and more effective treatment, as it also contains vWf.*

D – Diffuse low-level ST elevation means pericarditis. These patients often complain of pleuritic chest pain, which is somewhat alleviated by sitting up and leaning forward, and have distant heart sounds. Common test causes include viruses, uremia, and 2-3 weeks after myocardial infarction (Dressler syndrome). *

Block 3

E – Profuse super-watery diarrhea means cholera (the so-called “rice water stool”). That said, regardless of the cause, you treat all causes of volume loss with volume replacement (normal saline)!

D – Torticollis is a type of focal dystonia, which is a type of EPS (extrapyramidal symptoms) caused by neuroleptics (antipsychotics), such as haloperidol. Uncontrollable facial grimacing is a description of tardive dyskinesia, a rarer sometimes permanent EPS more associated with long-term antipsychotic use.*

C – That’s a litany of symptoms with only one reasonable single possible cause out of the provided choices: hyperthyroidism. Elevated thyroid hormone can manifest as anxiety, GI hypermotility, tachycardia and a-fib, weight loss, heat intolerance, etc. Thyroid disorders are very high yield. Pheochromocytomas (choice E) can cause some of the same symptoms in an episodic fashion (more typically panic attacks, episodic severe hypertension, headache).

A – Narcotic use for acutely painful conditions is both reasonable and important. Short-term use (immediately post-surgical) does not lead to long term dependence. And yes, drugs addicts should also receive narcotics to control pain.*

E – The most important cause of papillary necrosis is analgesia [abuse] nephropathy, a type of kidney damage caused by long-term use of OTC pain medications. Ischemia from disruption of blood flow from the vasa recta causes necrosis and sloughing of the renal papilla. Hematuria and sterile pyuria are common.*

A – The genetic questions always seem to hinge on remembering (or deducing) that T in DNA is replaced by U in RNA.*

B – If you think about this logically, what we have here is a congenital intolerance to breastmilk: galactosemia, in which the body cannot convert galactose to glucose (resulting in an accumulation of Galactose 1-phosphate). They then list the findings and tests used to diagnose it. Lactose (the disaccharide in milk) is composed of glucose + galactose.*

E – Endothelial tight junctions’ permeability is increased in response to injury and inflammation, allowing migration of white blood cells and friends to the site of injury.*

E – Ventricular fibrillation is the most common cause of sudden cardiac death immediately after myocardial infarction. This is why we have AEDs all over the place now. Papillary muscle rupture classically occurs 2-7 days after an MI and results in massive life-threatening mitral regurgitation. Free ventricular wall rupture after an MI can result in cardiac tamponade. *

E – PPIs raise pH by preventing the normal secretion of HCl into the stomach by parietal cells. The body attempts to counteract this unnaturally basic gastric pH with compensatory hypertrophy. If our medications are moving a measured element beyond its set-point, the body nearly always tries to compensate.*

E – The whole afferent/efferent thing is worth knowing. When the efferent arteriole is independently constricted, the blood can get into the glomerulus but has difficulty getting out. So more blood spends a greater amount of time in the glomerulus being filtered: GFR up, filtration fraction up, but overall blood flow is decreased due to the increased resistance of the system as a whole.

A – Benzodiazepines (including alprazolam aka Xanax) are effective at treating anxiety conditions. Ideally, their use should be limited to bridge therapy awaiting the efficacy of safer less habit-forming maintenance medications like SSRIs and buspirone.*

C – If you don’t eat enough calories to run your metabolism, your body will mobilize its stores. We “burn” fat through fatty acid oxidation.

E – Chronic microcytic anemia in a patient with normal iron studies should make you think of thalassemia. β-Thalassemia minor is the most common and is typically quite mild. As there is decreased beta chain production, there is a relative excess of alpha chains.*

E – Tetracycline use during childhood is commonly associated with tooth discoloration, typically yellow-brown (sometimes described as gray).*

A – Adalimumab is the only TNF inhibitor on the list. The fancy targeted therapies are all monoclonal antibodies and thus end in ab.*

B – The arrow is pointing to a neutrophil (multilobed nucleus). Main fighter of the immune system in acute inflammation and bacterial infection (such as aspiration pneumonia). C5a is a chemotactic factor for PMNs.*

C – AIDS retinitis is caused by CMV (typically seen with CD4 count less than 50). Treatment is with ganciclovir.*

E – This patient has stress incontinence, a common complaint in women after vaginal childbirth, the risk of which increases with number of deliveries, the size of the baby, and use of forceps, etc. The pelvic floor muscles and urogenital diaphragm are innervated primarily by the S3-4 nerve roots.*

A – Chronic anovulation is a common cause of infertility. Long periods are often anovulatory, where lack of an LH surge leads to unchecked estrogen and prevents ovulation and the secretory and menstrual phases that follow, leading to chronic proliferative-phase endometrium and irregular menses, which can be long or short, often light (as only the endometrial tissue that outgrows its blood supply sloughs off).*

A – GBS comes from a mother’s colonized vagina and is the most common cause of neonatal sepsis. Women who are GBS+ should receive PCN prophylaxis prior to delivery to prevent exposure to the fetus during delivery.*

B – Psychogenic polydipsia (PPD) is associated with several psychiatric conditions, particularly schizophrenia. It is also sometimes felt to be secondary to the dry/cotton mouth seen with certain medications, including antipsychotics. Patients present with hyponatremia due to their excessive free water intake. In some cases, a water deprivation test is necessary to distinguish PPD from diabetes insipidus.*

A – Foot drop after compression in the lower leg = common fibular/peroneal nerve. Nerve compression syndrome = one reason why it’s important that casts not be too tight.*

A – The closer R is to 1, the more closely the data points should fit to a line. I think the NBME is trying to imply that I will have poorly controlled diabetes in the future.*

E – VEGF is a major tissue growth factor activated by injury, cytokine release (infection, inflammation) and hypoxia that promotes angiogenesis and also increases vascular permeability (hence the edema). This increased permeability aids in the movement of proteins and white blood cells to the site of injury.*

C – In this question, they have described the components of congenital rubella. The distributed purpura (a result of extramedullary hematopoiesis) is a description of the classic “blueberry muffin rash” (which you are highly unlikely to hear actually described as such on a test).*

B – Fatigable weakness, particularly of the eyes, is classic myasthenia gravis, an autoimmune condition cause by antibodies that block acetylcholine receptors at the postsynaptic neuromuscular junction. The arrow is pointing to the patient’s prominent thymus. Thymoma and thymic hyperplasia are both in common in the patients with MG, and thymectomy is curative in a portion of patients. Small cell carcinoma of the lung is associated with Lambert-Eaton myasthenic syndrome, a disease caused by autoantibodies against presynaptic calcium channels. These patients classically begin weak and an experience a “warm up” effect after some use (they ultimately become weak again though).*

A – Renal artery stenosis causes decreased blood flow to the supplied kidney, which results in the activation of the Renin-Angiotensin-Aldosterone System, because the hypoperfused kidney secretes renin from the juxtaglomerular cells. The normal kidney has normal renin secretion. However, the additional circulating aldosterone will cause the normal kidney to retain sodium/water.*

E – Tons of exercise followed by renal failure is always going to be rhabdomyolysis. Dark urine (without actual blood in it) is due to myoglobinuria, which can cause a false positive urine dipstick.

A – In additional to thyroid problems, amiodarone can cause interstitial lung disease, including potentially fatal non-reversible pulmonary fibrosis. Digoxin is famous for its narrow therapeutic range and numerous side effects, including green-yellow vision changes. Lisinopril can cause angioedema, as well as hyperkalemia. Metoprolol can exacerbate asthma in addition to causing dizziness, bradycardia, and hypotension. Procainamide can cause drug-induced lupus.*

E – Delayed separation of the umbilical stump is a classic clue for leukocyte adhesion deficiency. ICAM is the defective ligand most often asked about as a second order question.

A – This patient has Conn’s syndrome (primary hyperaldosteronism), most commonly caused by a hyperfunctioning adrenal adenoma. This is an important and highly tested cause of refractory hypertension. The patient has lab abnormalities consistent with high aldosterone (high sodium, low potassium, metabolic alkalosis) with an appropriately suppressed renin.*

E – A chronic “heaped up” ulcerative lesion of the skin, especially on sun-exposed areas in people who spend time outdoors, means cancer. If it’s keratinocytes at play (and not melanocytes), that leaves you with either squamous cell or basal cell carcinoma.

B – Alcoholics (and any person with an altered level of consciousness) are a set-up for aspiration pneumonia: classically RLL, classically foul-smelling. The organism on tests will be Klebsiella.

D – Cholesterol xanthomas, horrible serum cholesterol levels, and early death by MI are all signs of familial hypercholesterolemia (caused by a defect in the LDL receptor).

E – All of the congenital heart defects and their associated murmurs are high-yield and worth memorizing. Understanding murmur physiology is also high yield in general. In this case, we have a cyanotic heart condition in a newborn. Tetralogy of Fallot is the most common cyanotic heart lesion on tests and in real life. ASDs–fixed split S2–are left-to-right (non-cyanotic lesions), at least until they reverse down the line (Eisenmenger syndrome). Clinically significant PDAs are alluded to by their continuous “machinery” murmur.

E – This is what a correlation is. A negative r-value means that the relationship between the variables is inverse (not direct), so as one goes up, the other goes down.*

A – An annular pancreas occurs when the pancreas is wrapped around the second (descending) portion of the duodenum. When symptomatic (in adults, typically when there is superimposed pancreatitis), it can block flow of GI contents through the intestines.*

B – The left sided system is much higher pressure than the right side, hence the aortic valve closing is usually louder than pulmonic valve. A P2 louder than A2 means that the pulmonary artery pressure is significantly elevated.*

E – Calcium oxalate stones are the most common variety of kidney stones, but uric acid stones make up 5-10% as well. None of the other choices are associated with renal calculi of any variety.*

E – The patient’s chronic inflammatory pneumonitis is killing off his lung parenchyma (composed primarily of type I pneumocytes). Type II pneumocytes, in addition to making surfactant, can replicate in order to replace type I pneumocytes, so they will be increased. Chronic interstitial inflammation results in fibrosis, hence an increase in fibroblasts.*

H – Furosemide is the prototypical “loop” diuretic, which works by blocking the triporter and preventing the reabsorption of 1 K, 1 Na, and 2 Cl ions. So less K/Na/Cl ion transport causes decreased osmolarity of the medullary interstitium (where these ions would normally enter). Water follows solute, so with less ions reabsorbed, less water will be reabsorbed.

B – Surgical portosystemic shunts are most often performed by anastomosing the splenic vein to the nearby left renal vein. The splenic and SMV join to form the main portal vein. are portal system veins. More commonly, a TIPS procedure is performed to create an intrahepatic shunt between the portal and hepatic veins.*

C – If an adult is taking on behaviors common to children, it’s called regression (don’t feel bad if it’s something you might do yourself).

Requests for further clarifications etc can be made in the comments below.

Question NO: 18 in block 1 THere are two choices that have samples with all appearance the same. Choice A and D. I have selected choice D thinking the same principle. but how do you differentiate choice A & D to come to Choice A as the right answer?

Others may disagree, but I think they are overall very similar. There may be a slightly greater proportation of easy questions, but the real Step exam (unlike UWorld) is actually full of easy questions too. It’s just that it’s also peppered with ridiculous questions, which when paired with the moderate difficulty questions leaves test takers feeling very uneasy during the big day.

Thank you so much for taking the time to explain all these answers. Makes studying them so much better!!! you are awesome. Also, its great to know that these are representative of the real exam. You just gotta keep ur cool when you get those ridiculous questions.

You’re welcome, and good catch! Both the infraspinatus and supraspinatus are innervated by the suprascapular nerve. That was an errata (now fixed). Knowing that the infraspinatus muscle is actually innervated by the suprascapular nerve is an especially testable fact (because it is somewhat counterintuitive).

I’ve heard both. I recall it being pretty accurate / slight overshoot when I used it myself. Any of those methods is going to both over and undershoot a bit just by merit of it being relatively short and having a big standard deviation.

Just checked again, looks consistent. Note that on the sample they provided, the right side of the brain is actually on the right of the screen (not flipped to the left like a radiology study would be). So this left sided brain stem lesion causes a left-sided (ipsilateral) cranial nerve finding with right-sided (contralateral) extremity findings. Does that answer your question?

If this were a CT or MRI, B would be the right pyramid and C the left. But notice that this histology slice actually has the sides labeled explicitly in the upper corners (left on the left, right on the right).

On the test I picked B on question #20 of the first block, but know that I am studying I’m thinking that it says “alpha hemolytic” and PSGN is due to the B hemolytic S. pyogenes, so now I am confused. By the way thank you for taking the time to explain the answers, I appreciate it a lot.

The platelet count in the patient’s serum is low, you’re correct. However, the bone marrow biopsy shows appropriately increased production: “bone marrow smear shows mature megakaryocytic hyperplasia.” This distinguishes the patient’s thrombocytopenia as a consumptive process and not a production issue (such as would be seen with bone marrow infiltrative diseases like myelofibrosis, for example).

H pylori causes stomach ulcers as described above: the bacteria creates a toxic microenvironment as it penetrates the mucosa via proteases and uses urease to actually raise the local pH in order to survive (not lowers it). It’s local damage that predisposes to gastric ulcer development, not the lower pH itself.

The subsequent hypersecretion and lower pH is what is responsible for downstream duodenal ulcers that are also associated with H pylori infection.

When you think of pure hyperacidity itself causing gastric and duodenal ulcers, on tests this most frequently is referencing the Zollinger-Ellison Syndrome.

The picture (I know I said you could ignore it, but it shows organisms)

also lol at the “rural boy” = plays in mud. I’ll add that to my list of USMLE stereotypes (right along with all black women have sarcoidosis, teenagers are promiscuous, & the homeless are always alcoholics….)

Hey Ben! These explanations have been great! Thank you so much for doing them! I was wondering if you could do a quick clarification on the 5 remaining questions that have the videos and heart sounds attached to them. They are unavailable on the PDF version of the practice questions, but you can download the practice exam and use the same software that you will see on the actual day of the exam! Sorry if this is confusing. But there was a 5 question segment that had a heart sound question and some videos, and it would be great if you could explain those as well! If you need clarification let me know!

I know of the extra questions but haven’t typically gone through them (partly because I can’t use the software on my primary computer, which is a Macbook). I’ll see if I can get to them at some point soon.

The explanation for #74 is incorrect. The math worked out in your favor, but OR is (a/c)/(b/d)…thus (100/300)/(200/300) = 0.5 ….the math you presented was going in the direction of RR, but with incorrect denominators.

Not quite. The math working in my favor is not a coincidence; it’s algebra (the exposure odds ratio and the disease odds ratio are equivalent). The cross products tell the story. Yours: (A/C)/(B/D) = (A/C)*(D/B) = AD/BC. My version (what some might intuitively refer to as the ‘disease odds ratio’) is (A/B)/(C/D) = (A/B)*(D/C) = AD/BC. The math is same. This is why I tend to think about these questions intuitively instead of just applying a formula. I’m dividing the odds of having cancer given statin use. You’re dividing the odds of taking a statin given having cancer (the exposure odds ratio). I think this page is helpful.

First Aid is correct, clarified above. Rule of thumb is that the medial side drains directly to the superficial inguinal group (along the greater saphenous vein), the lateral stops off at popliteal first.

Very helpful! Thank you very much!! I appreciate all you’re hard work. I got 75% on this and 82% on the Prometric practice exam (which had some of the same questions). Do you have any idea what that would mean for a 3 digit score? My exam is in one week, I have been averaging low 60s on Uworld blocks but I only got a 200 on NBME 16 that I took last week. I am scared a may fail.

There is no actual data for the free 150 (and it would vary every so often, of course). I’d guess ballpark 75-80% corresponds to around a 215-230. 60% on UW is also around a 225 last I checked, so that’d be concordant.

I don’t think there are any detailed explanations for any of the NBMEs that I know of. Your best bet is to google each individual question you’re curious about; a portion of them have been discussed on various internet forums.

Hi Ben, you are truly amazing. It helped me out so much to have your explanations while doing the review of the questions. It was a total difference to reviewing the NBMEs by myself. It surely saved a lot of time. Thanks!

For Gout = Examination of joint aspirate shows negative birefringent crystals correct? Could you discuss this question again? Thanks. Question #85 A 30-year-old man with peptic ulcer disease suddenly develops pain, redness, and swelling of his right first metatarsophalangeal joint. There is no history of injury. Serum uric acid concentration is 8 mg/dL. Examination of joint aspirate shows birefringent crystals. Which of the following drugs is most appropriate to treat the acute symptoms in this patient? (A) Allopurinol (B) Colchicine (C) Morphine (D) Probenecid (E) Sulfinpyrazone The normal reference ranges for uric acid are as follows: Men: 2.5-8 mg/dL

They merely said “birefringent,” they didn’t actually specify negativity/positivity. The purpose of that line is to tell you that this is a crystal arthropathy and not something else. That leaves you with gout and pseudogout. The first MTP location is classic for gout (“Podagra”) and is often the presenting flare. As described above, allopurinol is used an a preventative therapy to reduce the frequency and severity of attacks. It is not antiinflammatory but reduces serum uric acid production (note: a “normal” serum uric acid does not exclude gout). Colchicine or NSAIDs are used to treat acute gout flares.

Ive heard that taking STEP at different locations can lead to more “lenient” or tough curves. That its mainly tougher curves around where more Med Schools are close to the centers and what not (meaning to go take the exam at a center in Arkansas or something). Have you hear anything similar or might this be one of the more fictional rumors?

That sounds like BS to me. Among other things, it wouldn’t be the density of schools or takers but the quality/average score of the students taking it. So you should find a location with the “worst” medical school in the country and take it there. But no, I don’t think that’s true. The exam is standardized/normalized, and I believe this is done at the national level. I have heard that the standardization does vary by date, so that taking it early vs late in the season may be done via a different group, but I doubt this results in anything meaningful (the NBME knows how questions are likely to perform based on prior testing, so they’re not flying blind). Remember, it’s not as though the average score is always the same every year. So just take when and where is best for you.

Very true very true. When I first starting hearing things like this my jaw dropped at how many theories have been concocted. lol. Its hard to determine what to brush off and what to take as serious advice.

But overall, its all in how YOU prepare and all on getting those questions right :)

Thank you Ben, you are very awesome to have this here and have put in work to help out fellow docs. :) Bless you

I took the Prometric version recently that had a rather ambiguous heart murmur question. A teenage boy presented for a routine sports physical w/ non remarkable h/x minus a tonsillectomy d/t recurring otitis media as child. The media player allowed for auscultation of each valve. Sounded like mitral stenosis but Normal was also an option.

If it sounds like MS, then it’s probably MS as caused by rheumatic heart disease secondary to prior rheumatic fever. The history of tonsillectomy is often a subtle tip-off of multiple prior episodes of strep throat or tonsillitis. So if that’s what the murmur sounds like, that answer choice sounds reasonable. Given the lead time to the development of MS, a teenager is about as you as you can be and get MS from RHD.

Two common normal murmurs to exclude in kids are the Still’s (innocent) murmur, which is “musical” and systolic and the venous hum (constant low holodiastolic). Both of these should be distinguishable from mitral stenosis. While many systolic murmurs are benign, diastolic murmurs are uncommon and require workup (except for the obvious venous hum cases).

Hi Ben , regarding Q 50 ( aspirin toxicity ) . In early stages it starts off as respiratory alkalosis and then it becomes mixed respiratory alkalosis along with metabolic acidosis . What is the time line of “early” and “late” .I missed this question in the exam because according to UW 3 hrs is the borderline of both or so I remembered so I went with pure respiratory alkalosis .Is there any hint in the Q I could have picked up ?

I just rechecked 4-5 hrs is mixed and this question had 3 hrs and the pt was hyperventilating so I went with the obvious >> respiratory alkalosis choice C but I stayed confused about Hco3 would it go up or down .It should stay the same because renal compensation doesnt happen that early but that was not an option so at the end I was stuck between the timeline and the ABGs

I’ve read 3 hours for mixed, but more importantly, I think you’re overthinking it. I don’t think you’re ever going to see a question in real life that hinges on that; ASA toxicity questions are most likely to test if you know the classic mixed metabolic acidosis/respiratory alkalosis. Bicarb down, pc02 down, and pH down (though mixed, the metabolic acidosis tends to dominate).

Note that C is wrong no matter what. Bicarb going up would be metabolic alkalosis, which you would see neither in ASA overdose nor as compensation for respiratory alkalosis. In this case, you’re chasing the pH because you want the patient to be alkalotic, but the answer choice is internally inconsistent.

There’s a uworld question that indicates that aspiration of gastric contents would only have H. pylori. How does aspiration of gastric contents have Klebsiella? Can Klebsiella colonize the stomach? Also, FA says aspirate in the lower lobe wouldn’t be in the superior part of the lower lobe…

Where the aspirate goes depends in part on how the person is oriented when they aspirate (i.e. gravity). When upright, the classic RLL for example. But if supine (like an alcoholic who has passed out, then aspirated), then superior parts of the lower lobes (usually posterior) are often the paths of least resistance.

The “case series” study design has nothing to with observation vs intervention. Case Series typically follow a group with a known exposure or after a specific intervention (but always without a control group). You’ve heard of a Case Report (which might be, for an example, an interesting case on the medical ward or a novel surgical approach to a problem). A Case Series is essentially a multi-person Case Report.

If you read the question again, you’ll see that is not what is described. The subjects do not serve as their own control; they merely receive the treatment (in addition to what they were getting normally).

Thank you so much! I don’t know why I am not improving on my NBMES. I am failing them but I am doing great on these questions. Any tips to improve NBMES? Have taken Kaplan, DIT. When people say I’ve read First Aid, do they mine memorize it?

They basically mean to memorize it if possible, yes. To know how to best improve, you have to figure out why you’re getting questions wrong. Is it because you don’t know the facts or because you have trouble applying your knowledge to questions. If the former, are there specific areas in which you are weak? It’s usually a combination, but if it’s mostly the latter, then you’d likely want to focus on UW.